6.4　Piping Layout for Vacuum Service

6.4.1　Pressure drop calculation shall be made for the piping for vacuum service segment by segment，and the piping for vacuum service shall be routed for the shortest practical run with minimum number of elbows.

6.4.2　Check valves shall be located upstream of shutoff valves in vacuum pump suction.

Where standby pump is needed，the service pump and standby pump may share one check valve in the header.

6.4.3　The steam piping dedicated to steam ejector pump shall not be connected with the steam piping for other services，and a separate steam piping shall be routed to its steam ejector pump.

6.4.4　Condensate drain pipe（barometric leg）of inter-stage condenser for multi-stage steam ejector pump should not be shared，and separate atmospheric leg shall be provided for each stage of the steam ejector pump.

Barometric leg should be vertically inserted into knock out drum；otherwise，less than 45° elbow may be used to change piping run direction.

The height of barometric leg shall be calculated and determined based on the minimum absolute pressure expected during operation and shall not be less than 10m.

Valves shall not be installed in barometric leg.